performance overhead for setters and getters in Android?

When I was learning Java standard edition, getter and setter functions were often used to hide variables and to reduce direct access to them. I have been told by several sources that in Android you should not use these functions and only modify the variables directly. The reason is that there is a performance loss due to overhead when using getters and setters is used in Android. Resulting in more memory use and slowing down the system.

Is there any truth to this? and if there is, why the performance loss for using getter and setter?